Engine starter gearing



l March 19,1946.A D L MlLLER 2,397,033

ENGINE STARTER GBARING Filed Das. 2,l 1944V Patented Mar. *19, 1946Y ENGINE STARTER GEARING Donald L. Miller, Pine City, N. Y., assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application December 2, 1944, Serial No. 566,291

9 Claims.

The present invention relates to engine starter gearing and more particularly to that type of automatically engaging and disengaging drive which is arranged to maintain the gearing in mesh until the engine is reliably self-operative.

It is an object of the present invention to provide a novel starter drive in which engagement of the gearing takes place in response to acceleration of the motor shaft, and such engagement is maintained as long as the starting motor is energized.

It is another object to provide such a device in which the means for maintaining the engagement of the gearing is positive in action While involving no frictional or other contact with extraneous devices.

It is another object to provide such a device including Yoverrunning connection between the starting pinion and the motor.

It is another object to provide such a device including means for blocking the demeshing movement of the starting pinion, which blocking means is retracted responsive to the opening of the starting circuit.

It is another` object to provide such a device in which the blocking means is held in retracted position by a detent which is released when the starting switch is closed.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a side' elevation of a starter drive constituting a preferred embodiment of the invention with the remaining elements of the starting system shown diagrammatically;

Fig. 2 is a similar View of the starter drive in cranking position, and

Fig. 3 is a similar view of the starter drive show` ing the parts in the positions assumed after the engine has started and the starting pinion is overrunning the drive while remaining in mesh with the engine gear.

In Fig. 1 of the drawing there is illustrated a power shaft I which may be the extended armature shaft of a starting motor indicated diagrammatically at SM. A starting pinion 2 is slidably journalled on a. reduced smooth extension 3 of the power shaft I for longitudinal movement into and out of mesh with a gear 4 of an engine to be started. Means for actuating the pinion from the motor shaft are provided including a screw shaft 5 nxed on the end of 'the power shaft I as by means of a cross pin 6, and having a control nut member 1 threaded thereon.

Yielding means for connecting the nut 1 to the pinion l are provided comprising an annular member 8 of elastically deformable material such as rubber surrounding the nut 1 and seated at one end against a radial flange 9 ofsald nut. The opposite end of the elastic member 8 is seated in a thimble member I0 which is keyed as indicated at II within a barrel member I2. Said barrel encloses the elastic member 8 and bears at one end on the flange 9 vof control nut 1, beingretained thereon by any suitable means such as an internal ange I3. Thimble II has a cylindrical portion I4 bearing on the exterior of the control nut 1 and having telescoping ilt thereon so as to enclose the elastic member 8 and exclude foreign matter from the screw shaft.

A clutch member I5 is keyed in the barrel I2 adjacent the thimble I0 and is provided with teeth I6 adapted to engage teeth I1 on a flange member I8 ilxedly mounted in any suitable manner on the starting pinion 2. A dished spring member I8 is arranged to normally separate the clutch member from the pinion, the degree of separation being limited by a ring member or ferrule 2l which is crimped in the end of the barrel I 2 so as to retain the thimble I I' and clutch member I5 therein, and has an inturned ange 22 which overlaps the flange member I8 of the pinion 2, a thrust ring 23 being preferably interposed therebetween.

Anti-drift means for yieldably holding the pinion 2 and its associated parts in idle position is provided in the form of a detent 24 mounted-for radial movement in the control nut 1, and yieldingly pressed into frictional engagement with the screw shaft 5 by suitable means-such as a spring ring 26. The screw shaft 5 is preferably provided with an inclined shoulder 21 (Fig. 3) adjacent the idle position of the detent to cooperate therewith in resisting longitudinal movement of the control nut.

According to the present invention, means are provided `for holding the starting pinion 2 in partial mesh withr the engine gear 4 as long as the starting system is energized. As here shown this means comprises a blocking nut member 28 which `is threaded on the screw shaft 5 by means of threads 29 which are of the oppositehand to the threads which cooperate with the control nut 1. 'I'he blocking nut 28 has a cylindrical extension or sleeve 3I fixed thereon in any suitable manner which sleeve is arranged to engage the ange 9 of the nut 1 and prevent backward movement thereof.

A spring 32 'located between the blocking nut 28 and a flange member 33 ilxed on the end of the .prevents the control nut "l from demeshingthe pinion 2, as shown in Fig. 3.

Means are provided for controlling the action of the blocking nut 28 in accordance .with energization of the starting system. Aseshown in grounded at 36 and connected by a lead 31 to an electromagnetic starting switch indicated generally by numeral 38. The starting switch com' ,prises fixed contacts 39 and 4I adapted to be connected by an insulated *bridging contact 42 mounted on a magnetic plunger 43 which is arranged to be actuated by a solenoid 44 against the action of a spring 45. Contact 4I is connected by a lead 46 to the starting motor SM which is grounded at 41 to complete the -starting circuit. Solenoid 44 is energized from battery 35 through a manually operated control switch 4B closure of which causes the solenoid to actuate the plunger 43 to close the starting switch to thereby energize the starting motor.

The plunger 43 is provided with an extension 49 which is so positioned as to bear frictionally on the exterior of the sleeve 1li of the blocking nut 28 when the starting switch is opened. The sleeve 3I is provided with a circumferential channel I which is in registry with-the end of the plunger 49 when the blocking nut is retracted as shown in Fig. l whereby the blocking nut is` retained in retracted position as long as the start ing switch is opened.

In operation of the device, starting with the parts in normal position as shown in Fig. i, closure of the manual switch d8 energizes the solenoid 44 causing closure of the starting switch 38 and drawing the end of the plunger 49 out of contact with the sleeve 'Si of the blocking nut. The energization of the starting motor causes the control nut I to be threaded along the rotating screw shaft 5, carrying with it the barrel I2 and the starting pinion 2 until the latter has entered into mesh with the engine gear il and its travel is arrested by thrust rings'i seated against the shoulder formed by the reduction in diameter of the power shaft I. Further movement of the control nut 'l causes the clutch member I5 to engage its teeth with the teeth Il of the pinion flange I8, and then to compress the yielding member 8 until the torque transmitted through this member becomes sufficient to rotate the engine gear.

During the period of acceleration of the power shaft I,v the blocking nut 2li is held back in its idle position by its inertia. When the power shaft is decelerated by the engagement of the pinion 2 with the stationary engine gear il, the blocking nut 28 is traversed on the screw shaft 5 into engagement with the stop ring 34 thereon, and is yieldingly held in such engagement by the spring 32 during the cranking operation.

When the engine starts, the acceleration of the gear 4 causes the pinion 2 to overrun the drive, which rotation is initially transmitted to the control nut I sufficiently to cause it to back away from the pinion and release the clutch teeth It, Il after which the pinion is permitted to overrun freely. Further backward movement of the control nut I however, is prevented bythe sleeve 3i of the blocking nut 28 as shown in Fig. 3. If the engine fails to continue self-operative, the reduction in speed of the pinion 2 causes the spring IS to transmit a frictionalretarding effect to the Fig. I the starting system comprises a.- battery energizing the solenoid 44 and permitting the starting switch 38 to open, whereupon the spring 45 presses the end 49 of the plunger 43 into frictional engagement with the periphery of the sleeve 3l of the blocking nut 28. The consequent retardation of the nut 28 causes it to thread itself back along the screw shaft .5 into idle position where it is retained by the entry of the detent plunger 49 into the groove or channel 5 I as shown in Fig. 1. At the same time, the deceleration of the screw shaft 5 causes the control nut 'I to also return to idle position carrying with it the barrel I2 and pinion 2.

It will be seen that the disclosed invention provides means whereby the starting pinion is maintained in partial mesh with the engine gear at all times that the starting system is energized, but is withdrawn therefrom when the starting switch is opened, irrespective of relative speeds of the parts and without the necessity of any frictional or locking devices which are extraneous to the drive itself. Although but one embodiment of the invention has been shown and described in detail, it will be understood that other embodiments are possible and that various changes may be made in the design and arrangement of the 'parts without departing fromthe spirit of the invention.

What is claimed is:

1. In an engine starter drive a power shaft a pinion slidably journalled thereon for movement into and out of mesh with a gear of an engine to be started, means for traversing the pinion including a screw shaft, a nut and a yielding connection between the nut and pinion, and means rendered operative by energization of the starter for preventing demeshing movement of the pinion comprising a member having a threaded connection with the power shaft, and means for advancing said member during cranking into the path of said nut to obstruct itsdemeshing movement.

2. An engine starter drive as set forth in claim l including further, means responsive to deenergization of the starter for retarding rotation of said obstructing member to thereby cause it to thread itself back to inoperative position.

3. In an engine starter drive a power shaft, a pinion slidably and rotatably mounted thereon, a screw shaft rotatable with the power shaft, means for traversing and rotating the pinion responsive to rotation of the power shaft including a control nut threaded on the screw shaft, and a blocking nut member on the screw shaft movable by deceleration of the screw shaft into the path of the control nut to prevent its return to idle position.

4. An engine starter drive as set forth in claim 3 including further means for decelerating the blocking nut member.

5. An engine starter drive as set forth in claim 3 including further means responsive to deenergization of the starter for retarding the rotation y of the blocking nut member.

trol member and an overrunning clutch for traversing and rotating the pinion responsive to rotation of the power shaft, a blocking nut member on the threaded shaft, spring means urging the nut member along the threaded shaft into the path of movement of the control member to prevent return of the pinion to idle position and means for causing the nut member to move back into inoperative position.

7. In an engine starter drive a power shaft, a pinion slidably journalled thereon for movement into and out of mesh with a gear of an engine to be started, a screw shaft fixed to the power shaft having oppositely threaded portions, means operative on acceleration of the screw shaft to move the pinion into mesh with the engine gear including a control nut threaded on one portion of the screw shaft and a barrel member connecting the control nut and pinion, and a blocking nut member on the oppositely threaded portion of the screw shaft movable thereon responsive to deceleration of the screw shaft into engagement with the control nut to hold the pinion in mesh with the engine gear.

8. In an engine starter drive a power shaft, a pinion slidably journalled thereon for movement into and out of mesh with a gear of an engine to be started, a screw shaft fixed to the power shaft having oppositely threaded portions, means operative on acceleration of the screw shaft to move the pinion into mesh with the engine gear including a control nut threaded on one portion of the screw shaft and means connecting the control nut and pinion for longitudinal movement in unison, a blocking nut member on the oppositely threaded portion of the screw shaft movable thereon responsive to deceleration of the screw shaft into the path of the control nut member so as to obstruct its movement back to idle position, a detent, and means for moving the detent into engagement with the blocking nut member to retard its rotation and thereby cause its return to idle position.

9. In an engine starter drive a power shaft a. pinion slidably journalled thereon for movement 'into and out of mesh with a gear of an engine to be started, a screw shaft fixed to the power vshaft having oppositely threaded portions, means `it from translation back to idle position, a detent, and means responsive to the deenergization of the starter for moving the detent into engagement with the second nut member to retard its rotation and thereby cause its return to idle posi- DONALD L.

30 tion. 

